Move Singleton and related structs to namespace base

chrome/browser/signin/signin_error_controller_factory.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/signin/signin_error_controller_factory.h"
 
 #include "chrome/browser/profiles/profile.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 
 SigninErrorControllerFactory::SigninErrorControllerFactory()
     : BrowserContextKeyedServiceFactory(
           "SigninErrorController",
           BrowserContextDependencyManager::GetInstance()) {}
 
 SigninErrorControllerFactory::~SigninErrorControllerFactory() {}
 
 // static
 SigninErrorController* SigninErrorControllerFactory::GetForProfile(
     Profile* profile) {
   return static_cast<SigninErrorController*>(
       GetInstance()->GetServiceForBrowserContext(profile, true));
 }
 
 // static
 SigninErrorControllerFactory* SigninErrorControllerFactory::GetInstance() {
-  return Singleton<SigninErrorControllerFactory>::get();
+  return base::Singleton<SigninErrorControllerFactory>::get();
 }
 
 KeyedService* SigninErrorControllerFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   return new SigninErrorController();
 }